Investigators on Friday followed a long trail of possible clues in New York City's Time Square bombing.

A bicycle-riding bomber was captured on surveillance video placing the explosive device by the military recruiting center. The video also shows the bomb as it exploded. No one was injured.

The video shows the device produced a sudden flash and a billowing cloud of white smoke. New York City Police say the bomb could have killed anyone nearby.

The explosion was powerful enough to do minor structural damage to the recruiting center. The blast left a gaping hole in the recruiting station's front window and shattered a glass door, twisting and blackening the building's metal frame. The FBI was analyzing forensic evidence collected at the scene, New York Police Commissioner Raymond Kelly said.

The video from the scene proved to be too dark, grainy and out of focus for authorities to get a good look at the cyclist. However, investigators were also studying other security videos. One video showed a man exiting a subway station about ten blocks away, carrying a bicycle, police said.

The commissioner cited other possible clues: a new bike discovered at about 7 a.m. in a trash bin a few blocks from the blast, and the sighting of a man on a bike near the scene moments before the explosion.

The man caught a witness' attention because he was riding slowly, wearing a backpack and a hooded jacket, Kelly said. The witness, who was buying a newspaper at the time, said the hood "pretty much covered" the rider's face.

Law enforcement officials were looking into the possibility that Thursday's attack was connected to several letters that arrived the same day at Capitol Hill offices. Authorities were also examining other bombings at two foreign consulates in Manhattan in the last three years.

News of the bomb upset native New Yorkers and tourists alike. It also heightened speculation that all three incidents were the work of a lone bomber. Some officials also spectulated that he sought out the bright lights of Times Square to make a statement.

Investigation Turns to Capitol Hill

Capitol police, the FBI and the U.S. Postal Inspection Service were investigating the letters sent to congressional offices. The letters included a photo of the recruiting station and the claim "We Did It," according to a Democratic aide who spoke on condition of anonymity because the matter is under investigation. The message was accompanied by what appeared to be a political manifesto railing against the Iraq war, and a booklet.

Capitol police said the envelopes went through the standard security process, which involves radiating incoming mail. It can easily take a week or more, making it likely the letters were mailed well ahead of the bombing.

The bombing appeared similar to two consulate explosions.

Last October, two small explosive devices were tossed over a fence at the Mexican Consulate. The resulting explosions shattered some windows. Police said they believed someone on a bicycle threw the devices.

At that time, police said they were investigating whether it was connected to a nearly identical bombing at the British consulate on May 5, 2005.

Those bombings involved dummy hand grenades packed with black powder as an explosive, Kelly said. He said investigators were working to determine whether similar powder was used in the Times Square blast, but he noted that the explosive used Thursday was carried in an ammunition box, rather than a grenade.

Similar ammunition boxes are readily available in Army-Navy surplus stores, Kelly said.

All three blasts also occurred between 3:30 a.m. and 4 a.m., another sign that all of the attacks may be related.